Saturday, March 9, 2013

Visual Display Terminals

Visual Display Terminals


A visual display terminal is a computer terminal which usually has a keyboard for input and a screen for output .

A visual display terminal is also called a visual display unit or VDU. Its speed for output may vary from 10 characters per second (on a slow serial line) to 960 characters per second or faster.

Facilities on the different models can include:

1- Editing data anywhere on the screen to send it back to the computer.

2- Printing at any chosen point on the screen.

3- Storage in the terminal of data no longer on the screen.

4- Local processing.

5- Graphics .

6- Variable-sized characters.

Advantage of a VDU over a typewriter terminal

1- Quiet

2- Usually faster-at least for a given price.

3- No paper wasted.

4- Sometimes better facilities for editing data locally (i.e. without using the computer).

Situations in which VDUs are used

1- In almost any interactive situation where a printing or other specialized terminal is not necessary.

2- Where high-speed display is needed.

3- Where noise would be annoying.

Examples of uses of VDUs

1- At an airport terminal checking on flights for passengers. Here no hard copy is needed. However, in a situation where flights can be booked at the terminal point it would be useful to also have a printing terminal available.

2- As an operator's console in a computer room. An operator's console is the device used by the operators to control the computer. In this situation a fast terminal is required, but no hard copy.